Simplify the following expression: $k = \dfrac{s^2}{ts - 5s^2} + \dfrac{3s^2}{ts - 5s^2}$ You can assume $r,s,t \neq 0$.
Explanation: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{s^2 + 3s^2}{ts - 5s^2}$ $k = \dfrac{4s^2}{ts - 5s^2}$ The numerator and denominator have a common factor of $s$, so we can simplify $k = \dfrac{4s}{t - 5s}$